Heater
The SPN1 is fitted with an internal thermostatically controlled heater for
protection against frost and condensation. The heater is mounted on the
shadow mask, which will transfer heat around the inside of the dome and
the top of the enclosure.
When power is applied to the heater supply cables, it works as follows:-
•
The heater current is controlled by a 4Hz pulse-width modulated
switch.
•
If the external temperature is below 0
°
C, the heater provides the full
power available (up to 20W at 15V).
•
Above 0°C, the power reduces smoothly to 20% at 5
°
C, and then
down to nothing at 33°C.
Heater control
0
10
20
30
40
50
60
70
80
90
100
-10
-5
0
5
10
15
20
25
30
35
4
Temp degC
H
eater
C
u
rr
en
t %
0
At zero wind speed the dome will remain snow and ice-free down to minus
20
°
C.
At 2m.s
-1
wind speed the dome will remain snow and ice-free down to
minus 10
°
C.
In air temperatures below freezing
the heater can consume 1.5A at 12V
DC. A 40 Ah battery will only last about one day, so for extended data
logging in cold climates, we recommended that you power the heater via a
12V DC supply powered from the mains.
Warning! Do not apply AC mains power to the SPN1.
10
z
Introduction
SPN1 User Manual v1.0
